I never had much luck growing sprouts in a Mason jar, mine always grew mold
right along with the sprouts.
I grow mine in a clay flower pot. Buy a new largish unglazed clay pot (you
know, that orangey kind of color). Mine is about the size of a saucepan.
Give it a good wash, then soak it in plain water over night. Plug the hole
in the bottom with a coffee filter or paper towel. Rinse your seeds/beans
and spread them over the bottom of the pot. (Use about 2 tablespoons less
seeds than you think you need, I *always* over do it.) Set it on a plate
on the counter and cover it with another. Peek at them every day, and pour
a little water on the bottom plate when you get the urge. You want the pot
to always feel damp, but you don't want your sprouts swimming. Depending on
the seeds/beans and your kitchen temperature, they are ready in 2-3 days.